1. Field of the Invention
The present invention relates to fine organic polymer particles and a method of producing the same, and particularly, to a method of producing maleimide group-containing polymer particles that can be applied to uses such as carriers for diagnostic medecines or medicaments, chromatographic carriers, viscosity regulators, resin molding materials, paint additives, crosslinking/hardening agents and cosmetic additives.
2. Description of the Related Art
Functional polymer particles such as deionized resins and chelating resins have been widely used as carriers for various chemical substances. Such functional polymer particles have various reactive groups on the surface of insoluble polymers. Functional polymers into which various active hydrogen-containing groups are introduced, such as a carboxyl group, hydroxyl group and a primary or secondary amino group, have been used in various applications.
In recent years, biological molecules such as nucleic acids, peptides and antibodies or synthetic molecules analogous to these biological molecules have been used in affinity chromatography, diagnostic medecines, inspection chemicals or the like by fixing these biological molecules to polymer particles while retaining the activity of these biological molecules. When polymer particles having high selectivity are used in this manner, it has been preferable to use those having a maleimide group that can form a selective and stable bond with an SH group contained in biological molecules or analogous synthetic molecules, and can reliably carry these molecules. In these applications, it is necessary for the polymer carrier to carry the desired amount of a substance uniformly and reliably, and also to be highly dispersible in aqueous solvents.
There are a few known examples of polymer particles having a maleimide group. For example, fine particles in which a phospholipid layer containing a maleimide group exists on the particle surfaces has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 11-106391).
Nonetheless, in this method, a maleimide group-containing phospholipid must be produced in advance by reacting a maleimide group-containing compound such as N-(6-maleimidecaproyloxy)succinimide with a phospholipid and purifying the resultant product by a method such as column chromatography. Moreover, because a phospholipid layer containing a maleimide group is produced through multistage treatment and then formed on nuclear particles such as magnetic particles, this method has drawbacks in that the process is very complicated and the resulting particles are physically weak. This is due to the fact that the nuclear particles are not chemically bonded with the maleimide group-containing phospholipid layer.
There is also an example in which polystyrene particles containing a maleimide group have been reported (see, for example, the 2001/2002 Fluka Company product catalogue, p. 909). However, the maleimide group is a strongly hydrophobic functional group having very poor dispersibility in aqueous media. Further, the amount of the maleimide group is 0.4 mmol/g or less, which is insufficient for a functional group used to attain the aforementioned objects.
There is a need for maleimide group-containing polymer particles which require neither special raw materials nor a monomer having a reactive functional group, thus being cheaper and safe. It is imperative that such particles require no complicated operation, have increased loading amount of the maleimide group making it easy to control the loading, be mechanically strong and have superior water-dispersibility. A method for producing such particles is also required.